Electricity generation setup
For the electrical performance evaluations, high purity, flexible graphite sheets with a thickness of 0.05 mm, a density of 1-1.5 g/cm³, and carbon content of 99.9% were used as electrode, making a sandwich structure of graphite-nutshell-graphite (G-NS-G). The high-purity graphite sheet was selected because of its non-polarization property and cost effectiveness. On top of that, these thin, flexible graphite sheets can be adhered to the surface of the NSs when wet. The top graphite electrode covers less than 20% of the entire top surface, allowing the available free surface for effective water evaporation. A unique 3D printed setup, illustrated in Figure-S 4, had been constructed for the reliable electric connection. A small drop of Deionized (DI) water (1 ml) was used as water reservoir. The nutshell-based WEGs were connected to the multimeter (Agilent 34411A, Keysight, USA), SourceMeter (model B2901BL, Keysight, USA) and Potentiostat / Galvanostat (Interface 1010 E, Gamry, USA) to record the output voltage and current.
Supporting Information :
Supporting Information is available from the Wiley Online Library.